Peaks broadening

Besides phase identification XRD is also widely used for strain and particle size determination in thin films. Both produce peak broadenings, but they are distinguishable. Compared to TEM, XRD has poor area resolution capability, although by using synchrotron radiation beam diameters of a few pm can be obtained. Defect topography in epitaxial films can be determined at this resolution. 

The peak broadening measured for a plate number characterization is the sum of the variances a) for the column and the chromatographic equipment used ... 

The plate height in chromatography, H, is a useful indicator of the rate of peak broadening. The local plate height at any point on a column is given by the following ... 

When columns of the same polarity are used, the elution order of components in GC are not changed and there is no need for trapping. However, when columns of different polarities are used trapping or heart-cutting must be employed. Trapping can be used in trace analysis for enrichment of samples by repetitive preseparation before the main separation is initiated and the total amount or part of a mixture can then be effectively and quantitatively transferred to a second column. The main considerations for a trap are that it should attain either very high or very low temperatures over a short period of time and be chemically inactive. The enrichment is usually carried out with a cold trap, plus an open vent after this, where the trace components are held within the trap and the excess carrier gas is vented. Then, in the re-injection mode the vent behind the trap is closed, the trap is heated and the trapped compounds can be rapidly flushed from the trap and introduced into the second column. Peak broadening and peak distortion, which could occur in the preseparation, are suppressed or eliminated by this re-injection procedure (18). 

The characteristics of the sorbent in the precolumn may lead to problems when coupling the two systems. Therefore, when the analytes are more retained in the precolumn than in the analytical column, peak broadening may appear, even when the analytes are eluted in the backflush mode (40). This has been solved with a special design in which the analytes retained in the precolumn are eluted with only the organic solvent of the mobile phase and the corresponding mobile phase is subsequently formed (40, 41). 

GC peak broadening Thick film column is used. Thick film should... 

From an analytical perspective, the presence of droplets can also lead to apparent chromatographic peak broadening and a loss of resolution and analytical performance. 

The matrix, which in most reported applications appears to be glycerol, may either be incorporated directly into the mobile phase pre-column or added postcolumn. If added to the mobile phase, its effect on the separation must be considered, while if added post-column, significant peak broadening may be observed. 

Giddings, JC Bowman, LM Myers, MN, Isolation of Peak Broadening Factors in Exclusion Chromatography, Macromolecules 10,442, 1977. 

Determined by inductively coupled plasma-mass spectrometry of acid digested catalyst samples Calculated from X-ray diffraction peak broadening at (101) foranatase and (110) formtile TiOa Mean particle diameter measured from transmission electron microscopy pictures of gold catalysts... 

Very recently Husain et al.(12) obtained an analytical solution to the integral equation describing peak broadening for a turbidity detector in the Mie scattering regime. 

A were packed. They were individually calibrated. All three 3000 A columns showed similar peak separation characteristics for particle sizes between 312 nm and 5TQnm. However, peak broadening was much larger for one of the 3000 A 0olumns. This column was discarded. Of the remaining two 3000 A columns, one was subjected to the following ... 

Calibration of each column one at a time results in the weeding out of those columns which have inadequate peak separation, excessive peak broadening and significant particle loss by entrapment in the packing. 

Also, peak broadening appeared to increase with increased concentration of n-heptane. It is quite possible that mobile phase composition and/or polymer type affects axial dispersion. 

Molecular Weight and Peak Broadening Calibration in Size Exclusion Chromatography... 

Herein are reported improved methods of molecular weight calibration where simultaneously, peak broadening parameters (a) are obtained through the use of multiple polydisperse molecular weight standards. There are two basic methods covered. The first and most reliable method employs the universal molecular weight calibration curve obtained using narrow MWD polystyrene standards. 

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